Addresses the problem from a mathematical point of view, and shows applications to geophysical data coming from surface patches from digital elevation models (DEM) of the Pyre´ne´es mountains at the border between France and Spain. The new method proposed here uses scale transformations, and is applied without any particular a priori knowledge of the data. Construction of these scale transformation families is proposed first and then the efficiency of this innovative approach is shown by applying it to real data.